At wits end...what would Jim do?

[fbc25el]

Could the water be from condesation from the exaust not geting hot enough?

[Chris]

I'd definitely say the plug was a problem- I've had that same thing happen to me so don't feel bad.

On the water, I find it hard to believe that it's reversion. Those tails are not only sill-long, they drop at a 45 deg angle. I would screw some fittings into each of those manifolds and pressure test them before you destroy a motor. The SM's are welded, not cast. One leaking weld...

[Tony]

The plug was the issue, the exhaust leak is sealed. I ran the boat for an hour on the hose and pulled off both risers, there was water laying in the bottom of both exhaust manifods and droplets scattered all over the insides of both manifolds and risers and no exhaust leaks on either side. I find it hard to belive that both manifolds could have bad welds and I would say that natural reversion is totally out of the question.


If the intake manifold was leaking water into the cylinders wouldnt the engine barely run, or at least run like ****?

[MOBILEMERCMAN]

I am thinking it is less reversion and more likely the manifold, tail piece or head. Pressure check manifold, you can do that with it in place. Pull spark plugs and flow water through motor and check for water leaking in manifolds or out plug holes. I would think if it was the intake you would have water in your oil too. One cylinder with a water leak can spread it across the intake to both sides.

Flow water through static motor and look at everything.

[Chris]

Water isn't going to leak from your cooling jackets into the intake tract of the manifold. When the intake leaks, it's almost always in ther back and it leaks into the crankcase. The cam that it would take to revert at idle and get water up tails that long would be a very radical solid roller with HUGE overlap- wouldn't idle under 1200 and would still be dropping cylinders up to 3K.

[Tony]

OK, I pulled all 4 manifolds and risers off the boat and pressure tested each manifold with a 65psi load of air for about 5 minutes, all 4 were fine. I then hooked up the risers to the well spigot at work which has fairly high pressure, I held the risers straight up and down so it would be impossible for water to enter into the exhaust tube uless it was leaking. All 4 risers were fine.

Last night I pulled the dipstick tube and there where no signs of water in the oil. Would running at idle on the hose for an hour even show much signs of water in the oil if the intake manifold was leaking? Also If I was sucking water into the cylinders wouldnt the engine idle like ****? Its running super smooth idleing around 850 rpm.

One thing I noticed while testing the risers is that the outsides almost instantly turned wet with condensation when I turned the water on. So with the engine running would warm/hot exhaust air flowing through the inside of the exhaust create massive amounts of condensation inside the system?

[Ratickle]

This is a question for the pros;

Wouldn't the plugs show white/? color if any water at all was getting back to the cylinder as would happen with reversion, or a leak??

[MOBILEMERCMAN]

Yes, some not sure about massive. That is why Gils have diffuser rings and the 496 have tabulators. They catch the dripping condensation and it evaporates off before falling in the engine. People often remove them looking for performance.

It seemed like yours was excessive from the pix. I don't know does your exhaust offer rings for condensation? I would call them. I think it is more a northern problem the water here is 85*

Flappers will help to keep from pulling some of it back.

[MOBILEMERCMAN]

Here is the gil if you are not familiar with it.

http://www.mercruiserparts.com/Show_...NIFOLD%2FELBOW

[Tony]

There are flappers inside the Hardin tips and a small anti reversion tab inside the tube just past the elbow.

[MOBILEMERCMAN]

Did they same people make your tail pieces as your exhaust? The gil rings are probably about 3/16 or 1/4 in lip. Pretty significant. I would call the exhaust company and ask for their suggestion. Can you take a pic of the inside of the elbows are they still off? If they are on don't bother. Were the heads ported? did you flow water through the motor and check for leaks? That may be the first thing the exhaust guys ask.

I feel for ya.

[Tony]

Yes, SM made the risers, risers are still off so Il snap a pic of them later tonight. One thing I noticed when I removed the risers right after running the engine is that there were water dropplets all over the inside of the elbow and down into the flange like the water had been blasting out of the heads with the exhaust air.

[Chris]

Yes, SM made the risers, risers are still off so Il snap a pic of them later tonight. One thing I noticed when I removed the risers right after running the engine is that there were water dropplets all over the inside of the elbow and down into the flange like the water had been blasting out of the heads with the exhaust air.

That's your next step. Fill the block up, plug all the openings and pressurize. Use a regulator- don't go over 25-30 psi.

[MOBILEMERCMAN]

Are the tail pieces dry on the other motor?

[Tony]

I pulled all the plugs and the #5 and #6 plugs were wet. I filled the engine with water and put 30 psi of air on it for over an hour and it didnt loose any pressure. Then I dumped the pressure and put tape pover the spark plug holes and cranked the motor. the 5 and 6 plugs had tiny amounts of moisture on the tape...

I ran the oposite motor and the end result was dry manifolds and dry risers, however one side was running about 30 degrees hotter than the other........

[MOBILEMERCMAN]

I don't know what 5 and 6 have in common. Which two are connected by exhaust cross over in manifold? Sorry, Nothing else immediately comes to mind to check. I will have to sleep on it.

The temp variation on a hose is normal on the other side. It should be close even in the water.

[MOBILEMERCMAN]

I am not sure why Chris suggested pressure checking with water in it. I have always pressure checked things dry. I guess it is to see the leak.

[Chris]

Doing it wet does two things. First, water leaves water behind when little bits seep out. Air blows away. Second, you still have a little bit of air in there and if you're losing pressure, that small volume of air causes the pressure to drop quickly. If the whole thing is full of air, it takes longer for the gauge to move.

[Chris]

Small block heads are notorious for cracks between the intake and exhaust seats. The water jacket is very close to ther seat.

[Chris]

I don't know what 5 and 6 have in common. Which two are connected by exhaust cross over in manifold? Sorry, Nothing else immediately comes to mind to check. I will have to sleep on it.

The temp variation on a hose is normal on the other side. It should be close even in the water.

5 & 6 are on opposite banks. Chevy is 1,3,5,7;2,4,6,8. Ford is 1,2,3,4;5,6,7,8.